In recent years, ubiquitous communications is provided with mobile terminal such as a laptop PC or a smart phone and a wireless network, such communications are becoming popular.
In addition, recent mobile terminals normally include a camera and a microphone, and also have a media processing function. Hence, a demand for communication services with multimedia information, such as videos and sound, which need a fast line speed are increasing.
Communication quality of a stationary communication, that is not a ubiquitous, is provided with such as an installed desktop PC and a wired LAN connection, such communication has little change in comparison with that of a ubiquitous communication.
Conversely, in the case of ubiquitous communication, failures, such as a communication delay and a communication disruption, due to a change in communication speed, radio wave condition, etc., originating from a change in location where the communication is utilized suddenly occur. In particular, this becomes a considerable problem that disturbs a smooth communication in multimedia information communication services with a high real-time characteristic like a video conferencing.
In order to provide a stable service through ubiquitous communication, it is desirable to always measure a changing communication quality, and to control a service communication based on the measurement result, thereby suppressing a failure.
When, for example, it becomes clear that, in a video conference service, the currently available upstream line speed is slower than the transmitting speed of currently transmitted video streams upon measurement of the communication quality, by decreasing the transmitting speed of video streams, failures, such as a transmission delay and frame dropping, are suppressible.
As an example conventional technology of measuring a communication quality in ubiquitous communication, and controlling the service communication, a scheme of utilizing a measurement result of the communication quality in the physical layer in an OSI reference model has been known.
For example, Patent Document 1 discloses an apparatus that changes a communication parameter with another communication apparatus based on the radio wave intensity in wireless communication.
As another example conventional technology of measuring a communication quality in ubiquitous communication, a scheme of measuring the communication quality in a transport layer has been also known, and this technology is applied in speed measuring sites over the Internet (see Non-patent Document 1). The speed measuring site is a website which measures, based on a result of data transfer between the PC of a user and the server of the speed measuring site, a line speed of a network to which the user is connected, and presents the measurement result to the user. According to typical speed measuring sites, a line speed is calculated based on the data size of a TCP payload transferred between the PC of the user and the server of the speed measuring site, and, a time needed for the transfer.
The data transfer to measure a communication quality in the transport layer and the data transfer for a service like video streaming have different characteristics. The data transfer to measure the communication quality attempts to transfer data with a large communication load in order to check the maximum communication quality. In contrast, the data transfer for the service does not always need the maximum communication quality.
When, for example, the communication terminal of the user has only the performance of decoding video streaming with a small data size, it is desirable not to receive video streaming with a large data size even if the line speed has leeway. Conversely, when the same terminal has the sufficient performance of decoding sound streaming, it is fine if the sound streaming is received at a fast speed by utilizing the maximum communication quality.